Car Mechanics’ Jargon for the Technically Challenged, Part Two

Bamboozled and befuddled by garage jargon? Tired of pretending you understand what your mechanic is going on about? Then you really need our garage jargon-buster. You should definitely check out Part One of this article first, then continue with the terms below.


We actually wrote an article on the DPF back in 2018 — you can see Part One here and Part Two here. But in short, DPF is short for Diesel Particulate Filter, which pretty much tells you what it does. This essential bit of kit forms part of the exhaust system on diesel cars, where it filters out tiny, health-damaging soot particles. Like any filter, the DPF periodically gets filled up and needs to be cleaned out. Fortunately, your vehicle’s software detects this and when necessary runs the engine through a cycle of activity designed to burn off the excess. This is called regeneration.

However, if regeneration doesn’t work correctly, you might need some intervention from a garage. So, when your technician tells you, “The DPF hasn’t regenerated,” he’s describing a simple problem, rather than quoting a line from Star Trek.

Excess Play

Obviously, excess play is something that happens whenever you get a brand-new games console. But it’s also something that describes mechanical bits and pieces moving more than they should. You hear it most often when a mechanic is discussing steering or suspension. Excess play sounds harmless, but it’s potentially serious. For example, excess play in the steering wheel — essentially looseness — can make the car more unpredictable and difficult to control. Often, excess play is a sign that components are wearing out, and it needs properly investigating.

Head Gasket

The main part of your engine – the block – has a top part called the cylinder head and a lower component, properly called the cylinder block. Between the two, there’s a thin layer that’s generally made from steel. This is the head gasket. It’s job is to provide a seal and to keep different fluids within the engine from mixing or leaking. If the head gasket fails, mechanics are fond of saying that it’s ‘blown’ or just ‘gone’. There are various signs that this has happened, including your exhaust pumping out white smoke, or your engine oil looking like some mayonnaise you found at the back of the fridge. Head gaskets are far more reliable than when they were made from asbestos (yes, really!), but can cause engine-destroying carnage when they fail.

Pressure Test

Your car’s cooling system does a fantastic job of removing all the excess heat which the engine is generating, keeping everything running at a safe temperature. If the cooling system starts leaking and losing fluid, you risk major engine damage. Unfortunately, leaks within the system can be hard to spot. Enter the pressure test. By pressurising the system, any cracks or leaks in the system (for example, in the cylinder head) can be more easily located.


The sump is an oil reservoir that usually sits at the bottom of the engine. It looks like something that could be used in baking, though we don’t recommend it. Oil is pumped up from the sump, through an oil filter and is used to lubricate the engine. It then drains back into the sump. Air flowing over the sump also helps cool the oil.

The sump is as tough as old boots, but it is possible to damage it if the bottom of the car grounds with enough force. A more likely defect is one of the drain plug washers needing to be replaced.

Once you achieve achieve boss-level jargon, you can start talking about dry sumps and wet sumps, both of which sound like medical conditions.


You’ll be relieved to hear that tracking is just another term for alignment, which we covered in Part One. Mechanics have been known to switch from one term to the other in the same sentence!

There’s plenty more mechanical jargon where these came from, but we hope that our quick glossary gives you a head start. And please, if you’re not clear on what we’re doing and why, just ask. All of our technicians have been specially trained not to bite!

The WVS blog covers a wide range of automotive topics, from the contentious to the light-hearted. We are an independent garage specialising in all the VW group marques, including Audi, Volkswagen, Skoda and SEAT. WVS provides services, repairs and MOTs, delivering a main dealer level of care at affordable prices. To book your vehicle in, or for any enquiries, get in touch.